A New Transition Wolf-Rayet WN/C Star in the Milky Way

TL;DR

This paper reports the discovery and detailed characterization of a new transition Wolf-Rayet star in the Milky Way, providing insights into its spectral type, physical properties, and likely single-star nature.

Contribution

The study identifies a new WN/C transition Wolf-Rayet star in the Galaxy and derives its physical parameters using spectroscopic and astrometric data, highlighting its likely status as a single star.

Findings

Located in the Far 3 kpc Arm, 7.11 kpc from Earth.

Spectral analysis indicates a WN7o/WC transitional subtype.

Physical parameters include a stellar mass of 7.1 M_solar, T_* = 47 kK, and a mass-loss rate of 10^(-4.97) M_solar/yr.

Abstract

We report the discovery of a new transition type Wolf-Rayet (WR) WN/C star in the Galaxy. According to its coordinates (R.A., Dec)J2000 = 18h51m39.7s, -05d34m51.1s, and the distance (7.11 kpc away from Earth) inferred from the second Gaia, data release, it's found that WR 121-16 is located in the Far 3 kpc Arm, and it is 3.75 kpc away from the Galactic Center. The optical spectra obtained by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the 2.16 m telescope, both located at the Xinglong Observatory in China, indicate that this is a WR star of the transitional WN7o/WC subtype. A current stellar mass of about 7.1 M_solar, a mass-loss rate of M_dot = 10^(-4.97) M_solar/yr, a bolometric luminosity of log L/L_solar = 4.88, and a stellar temperature of T_* = 47 kK are derived, by fitting the observed spectrum with a specific Potsdam Wolf-Rayet (PoWR) model. The magnitude in V-band varies between 13.95 and 14.14 mag, while no period is found. Based on the optical spectra, the time domain data, and the indices of the astrometric solution of the Gaia data, WR 121-16 is likely a transitional WN/C single star rather than a WN+WC binary.